Internal combustion engines and pistons therefor



June 12, 1962 w. P. MANSFIELD 3,038,458

INTERNAL COMBUSTION ENGINES AND PISTONS THEREFOR Filed Oct. 5, 1960 2 Sheets-Sheet 2 1 4 44 Jgfi i 20 5' Z aren't 3,038,458 Fatented June 12, 1962 3,638,458 INTERNAL CUMIEUSTIGN ENGIIIES AND PISTUNS TI-IEREFQR Wilfred Percival Mansfield, longh, England, assignor to The British Internal Combustion Engine Research Association, Slough, Engiand Fit-ed (let. 5, 196%, Ser. No. easzs Claims priority, application Great Britain Get. 9, 1959 5 Claims. (Cl. 1123-78) This invention relates to internal combustion engines and pistons therefor and comprises improvements in or modifications of the constructions described and claimed in my prior United States Patent No. 2,742,027, dated April 17, 1956, which is concerned in particular with a method and means for varying the clearance volume in a cylinder of an internal combustion engine having a crown portion and parts capable of limited relative movement defining a first chamber and a second chamber, such relative movement in one direction increasing the distance between the crown portion of the piston and the means for converting reciprocating movement of the piston into rotary motion of the engine output shaft and also increasing the internal volume of the first chamber and decreasing the internal volume of the second chamber whilst such relative movement in the other direction decreases the said distance and also decreases the internal volume of the first chamber and increases the internal volume of the second chamber, a supply passage adapted to receive substantially incompressible fluid, i.e. liquid, under pressure from a source external to the piston, a first inlet passage communicating between the supply passage and the first chamber, a second inlet passage communicating between the supply passage and the second chamber, a first non-return valve permitting flow of fluid through the first passage towards the first chamber, a second non-return valve permitting flow through the second passage towards the second chamber, a first discharge passage leading from the first chamber, a discharge valve controlling fiow of fluid from the first chamber through the first discharge passage, a second discharge passage leading from the second chamber and controlling the flow of fluid from the second chamber, and means for substantially preventing the flow of fluid from the first chamber into the second chamber or from the second chamber into the first chamber.

A number of embodiments are described in the prior specification mentioned above for use with four stroke cycle internal combustion engines in which the whole of the crown of the piston is variable in relation to the connection of the piston with the means for converting reciprocating movement of the piston into rotary motion of the engine output shaft whereby a variable piston bumping clearance is provided. This is unsuitable where a squish action is required.

The invention consists in a piston, for an internal combustion engine, of the kind adapted to vary automatically the clearance volume in the cylinder in which it works with change of maximum pressure in said cylinder by reason of having parts capable of limited relative movement which change the relative volume of a first and a second chamber containing a liquid and having means for controlling the movement of the liquid into and out of said chambers characterised in that one of said parts comprises the body of the piston while another comprises a part of the crown of the piston movable in relation to the body.

The accompanying drawings show by way of example only two embodiments of the invention in which:

FIGURE 1 is a view in vertical section of a first embodiment of the invention taken along line 1-1 of FIG- URE 4,

FIGURE 2 is a vertical cross-sectional view at right angles to the gudgeon pin of a second embodiment of the invention,

FIGURE 3 is a vertical cross-sectional view at right angles to the view shown in FIGURE 2 and thus through the axis of the gudgeon pin of the embodiment shown in FIGURE 2,

FIGURE 4 is a transverse cross-sectional view taken along line 44 of FIGURE 1, with parts removed and through the main piston body and illustrating the passage arrangement through which oil feeds past the non-return valves, and

FIGURE 5 is a fragmentary vertical cross-sectional view taken along line 55 of FIGURE 4 illustrating the feed arrangement and on-return valve that feeds oil to the upper space beneath the upper supplementary piston.

In the construction shown in FIGS. 1 and 4 the portion of the piston which moves relative to the gudgeon pin to vary the compression and expansion ratios is an upper supplementary piston 1 carrying sealing ring 2 and moving in a bore in the main piston crown. The upper supplementary piston 1 has a cylindrical stem 3 to which a lower supplementary piston 4, with piston ring 5, moving in a lower bore, is secured by means of a circlip. The upper space 16 below the upper supplementary piston 1 and the annular space 17 around the stem 3 above the lower supplementary piston 4 form upper and lower chambers performing the same functions as the first and second chambers in the corresponding constructions shown in said prior specification.

The oil flow is apparent from the structure shown in FIGURES 1, 4 and 5 thus, oil feeds up the channel in the connecting rod, FIGURE 1, around the gudgeon pin bearing, through channel 101 and into the space 11. Oil leaves this space and passes through bore 66, into the space around the stem of valve 6, past this valve, which is a non-return valve, and thence through bore 666 into the lower oil chamber or space 17 above the lower supplementary piston 4. In addition, as shown in FIGURES 4 and 5, oil from space 11 flows through bore 77 around the stem of valve 7, past this valve which, as is clear from FIGURE 4, is behind valve 6 and is similar to that valve, thence into the space 700 above the valve 7 and through bore 777 into the space 16 which is the upper oil chamber and is below the supplementary piston 1. The spring-loaded discharge valve 8 serves the upper chamber while the size of the discharge orifice 9 determines the rate of upward movement of the supplementary piston assembly.

The method of operation is the same as the corresponding embodiment shown in my prior United States Patent No. 2,742,027, dated April 17, 1956, above men tioned.

An annular oil cooling space, indicated by broken lines 10 may be cast in and be fed with oil by a passage leading from the space 11. The spring 12 in the space 11 not only serves to hold the oil collector 13 in position but also assists in bringing the supplementary piston assembly to the high ratio position when the engine is stopped.

A ceramic coating 14 is provided to protect the face of the upper supplementary piston and acts as a heat barrier. A second barrier may be formed by deepening the groove of the lower piston ring of the upper supple mentary piston 1 and filling the space 15 with heat insulating material.

The above embodiment is provided with its second chamber around the stem of the upper supplementary piston above the gudgeon pin in distinction from the corresponding construction shown in my prior United States Patent No. 2,742,027, dated April 17, 1956, where it is formed adjacent the skirt of the piston.

The crown may be made of a suitable ceramic material of which the mechanical strength is similar to cast iron and has good thermal properties.

The piston shown in FIGURES 2 and 3 is provided with a piston bowl 18 formed between an insert 19 screwed into the piston crown and the upper supplementary piston 1, which carries sealing rings 2 and moves in a bore in the insert 19.

This form of construction enables some very desirable cooling to be provided for the rings 2 without overcooling the top of the upper supplementary piston 1, by providing the groove 20 in the piston, which groove is closed by the insert 19 and is fed with oil from the common supply through the inlet passage 22 and out by way of the passage 21 to the sump of the engine.

The supply of oil to the pistons is by way of a channel shown in dotted line in the connecting rod, and is either a timed supply or an automatic non-return valve is provided in the supply line to prevent return flow of oil down the rod due to inertia forces.

It is to be understood that the above description is by way of example only and that details for carrying the invention into effect may be varied without departing from the scope of the invention claimed.

I claim:

1. A piston for an internal combustion engine, said piston comprising a first main part and a second main part axially movable with respect to said first main part, said first main part providing the body of the piston, means for connecting said first main part to a connecting rod, said first main part having a recess in the upper end thereof, said second main part providing an upper supplementary piston slidably received in said recess and forming a portion of the crown of the piston, said first main part having a second recess spaced inwardly from said first recess, a lower supplementary piston slidably received in said seocnd recess, means connecting said upper and lower supplementary pistons, a cavity in said first main part, means for conducting fluid from a passage in the connecting rod to said cavity, a first passage connecting said cavity and said first recess below said upper piston, a non-return valve in said first passage, a second passage connecting said cavity and said second recess above said lower piston, a non-return valve in said second passage, a third passage connecting said first recess below said upper piston and the exterior of the main piston at the lower end of said first main part, a pressure relief valve in said third passage and a restricted passage in said lower piston connecting said second recess above said lower piston and said cavity.

2. A piston as defined in claim 1 in which said first recess is provided with a removable insert providing a liner, said upper supplementary piston being slidably received in said insert.

3. Piston as claimed in claim 1 in which said upper supplementary piston forms the central portion of the crown of the piston and is movable relative to the peripheral portion of the crown.

4. Piston as claimed in claim 3 in which said upper supplementary piston is formed to provide a combustion bowl.

5. Piston as claimed in claim 1 in which said upper supplementary piston is provided with an axial stem which passes through and makes a sliding fit in a bore in the bottom of said first recess and has attached thereto said lower supplementary piston.

References Qited in the file of this patent UNITED STATES PATENTS 1,825,163 Schweter Sept. 29, 1931 2,104,802 Hansen Ian. 11, 1938 2,170,266 Leissner Aug. 22, 1939 2,742,027 Mansfield Apr. 17, 1956 

